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          <h1>OC中的各种遍历</h1>
     
        <div class="read-more clearfix">
          <span class="date">2018/5/8</span>

          <span>posted in&nbsp;</span> 
          
              <span class="posted-in"><a href='ios.html'>iOS</a></span>
           
         
          <span class="comments">
            

            
          </span>

        </div>
      </div><!-- article -->

      <div class="article-content">
      <blockquote>
<p>iOS开发中我们经常遇到各种的数据处理，所以就会经常遇到数组遍历 和 字典遍历。但是不同的遍历方式，效率不同，并且还有不同的限制。</p>
</blockquote>

<p>首先把数据源准备好：</p>

<pre><code class="language-text">_dataSource = [NSMutableArray array];
_dataDic = [NSMutableDictionary dictionary];
for (int i=0; i&lt;5; i++) {
    [_dataSource addObject:@(i)];
    [_dataDic setObject:@(i) forKey:[NSString stringWithFormat:@&quot;我是第%d个Item&quot;,i]];
}
</code></pre>

<span id="more"></span><!-- more -->

<h2 id="toc_0">for循环遍历</h2>

<h3 id="toc_1">遍历数组</h3>

<pre><code class="language-text">for (int i = 0; i&lt;_dataSource.count; i++) {
    NSLog(@&quot;%@ --- thread:%@&quot;,[_dataSource objectAtIndex:i],[NSThread currentThread]);
}
</code></pre>

<h3 id="toc_2">遍历字典</h3>

<pre><code class="language-text">// 取出字典中所有的key （无序的）
NSArray *keys = [_dataDic allKeys];

for (int i = 0; i&lt;keys.count; i++) {
    // 根据key值索引Value即可
    NSString *key = [keys objectAtIndex:i];
    NSString *value = [_dataDic objectForKey:key];
    NSLog(@&quot;%@ --- thread:%@&quot;,value,[NSThread currentThread]);
}
</code></pre>

<p>这是打印结果</p>

<pre><code class="language-text">2018-05-09 15:01:23.119707+0800 OCProject[78848:4457173] 0 --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.120003+0800 OCProject[78848:4457173] 1 --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.120262+0800 OCProject[78848:4457173] 2 --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.120473+0800 OCProject[78848:4457173] 3 --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.120754+0800 OCProject[78848:4457173] 4 --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.120951+0800 OCProject[78848:4457173] 我是第3个Item --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.121111+0800 OCProject[78848:4457173] 我是第1个Item --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.121231+0800 OCProject[78848:4457173] 我是第4个Item --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.121377+0800 OCProject[78848:4457173] 我是第2个Item --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
2018-05-09 15:01:23.121539+0800 OCProject[78848:4457173] 我是第0个Item --- thread:&lt;NSThread: 0x604000263b40&gt;{number = 1, name = main}
</code></pre>

<h3 id="toc_3">【分析】</h3>

<ul>
<li>优点：简单</li>
<li>缺点：遍历字典有太多中间变量，会有一部分开销</li>
</ul>

<h2 id="toc_4">for-in遍历</h2>

<h3 id="toc_5">遍历数组</h3>

<pre><code class="language-text">// 遍历数组
for (NSNumber *obj in _dataSource) {
    NSLog(@&quot;%@ --- thread:%@&quot;,obj,[NSThread currentThread]);

}
</code></pre>

<h3 id="toc_6">遍历字典</h3>

<pre><code class="language-text">// 遍历字典
NSArray *keys = [_dataDic allKeys];
for (NSString *key in keys) {
    NSString *value = [_dataDic objectForKey:key];
    NSLog(@&quot;%@ --- thread:%@&quot;,value,[NSThread currentThread]);

}
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">2018-05-09 15:17:28.993429+0800 OCProject[79116:4479093] 0 --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.993769+0800 OCProject[79116:4479093] 1 --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.993980+0800 OCProject[79116:4479093] 2 --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.994204+0800 OCProject[79116:4479093] 3 --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.994375+0800 OCProject[79116:4479093] 4 --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.994505+0800 OCProject[79116:4479093] 我是第3个Item --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.994693+0800 OCProject[79116:4479093] 我是第1个Item --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.994861+0800 OCProject[79116:4479093] 我是第4个Item --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.995037+0800 OCProject[79116:4479093] 我是第2个Item --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
2018-05-09 15:17:28.995253+0800 OCProject[79116:4479093] 我是第0个Item --- thread:&lt;NSThread: 0x60400006c0c0&gt;{number = 1, name = main}
</code></pre>

<blockquote>
<p>这里需要注意的是的  for-in 遍历时如果对数组进行增删操作会导致程序crash。</p>
</blockquote>

<h3 id="toc_7">【分析】</h3>

<ul>
<li>优点：
<ul>
<li>语法简洁</li>
<li>效率高</li>
</ul></li>
<li>缺点：无法获得当前遍历操作所针对的下标。</li>
</ul>

<h2 id="toc_8">枚举器</h2>

<h3 id="toc_9">遍历数组</h3>

<pre><code class="language-text">/*
 * 正向枚举：objectEnumerator
 * 反向枚举：reverseObjectEnumerator
 */
NSEnumerator *enumetorArr = [_dataSource objectEnumerator];
id obj ;
while (obj=[enumetorArr nextObject]) {
    NSLog(@&quot;%@ --- thread:%@&quot;,obj,[NSThread currentThread]);
}
</code></pre>

<h3 id="toc_10">遍历字典</h3>

<pre><code class="language-text">  NSEnumerator *enumtorValue = [_dataDic objectEnumerator];// Value枚举器 reverseObjectEnumerator反向顺序
  NSEnumerator *enumtorKey = [_dataDic keyEnumerator];// key 枚举器
  id value;
  while (value=[enumtorDic nextObject]) {
       NSLog(@&quot;%@ --- thread:%@&quot;,value,[NSThread currentThread]);
   }
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">2018-05-09 15:35:49.961318+0800 OCProject[79558:4515099] 0 --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.961554+0800 OCProject[79558:4515099] 1 --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.961666+0800 OCProject[79558:4515099] 2 --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.961788+0800 OCProject[79558:4515099] 3 --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.961909+0800 OCProject[79558:4515099] 4 --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.962030+0800 OCProject[79558:4515099] 我是第3个Item --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.962130+0800 OCProject[79558:4515099] 我是第1个Item --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.962257+0800 OCProject[79558:4515099] 我是第4个Item --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.962369+0800 OCProject[79558:4515099] 我是第2个Item --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
2018-05-09 15:35:49.962485+0800 OCProject[79558:4515099] 我是第0个Item --- thread:&lt;NSThread: 0x604000065300&gt;{number = 1, name = main}
</code></pre>

<h3 id="toc_11">【分析】</h3>

<ul>
<li><p>优点：对于不同的数据类型，遍历的语法相似；内部可以简单的通过reverseObjectEnumerator设置进行反向遍历。</p></li>
<li><p>缺点：代码量稍大。</p></li>
</ul>

<h2 id="toc_12">快速枚举遍历</h2>

<h3 id="toc_13">遍历数组</h3>

<pre><code class="language-text">// 按照顺序来的
[_dataSource enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    NSLog(@&quot;sort:0 %@ -- %lu --- %@ --- %@&quot;,obj,(unsigned long)idx,stop?@&quot;YES&quot;:@&quot;NO&quot;,[NSThread currentThread]);
}];

// 随机的顺序遍历,开启了多个子线程  NSEnumerationReverse反向遍历，并发遍历 NSEnumerationConcurrent 开启了多个子线程
[_dataSource enumerateObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    NSLog(@&quot;sort:1 %@ -- %lu --- %@ --- %@&quot;,obj,(unsigned long)idx,stop?@&quot;YES&quot;:@&quot;NO&quot;,[NSThread currentThread]);
}];

 // 指定循环范围 ，循环次数多可以开辟子线程
[_dataSource enumerateObjectsAtIndexes:[NSIndexSet indexSetWithIndexesInRange:NSMakeRange(0, _dataSource.count)] options:NSEnumerationConcurrent usingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
    NSLog(@&quot;sort:2 %@ -- %lu --- %@ --- %@&quot;,obj,(unsigned long)idx,stop?@&quot;YES&quot;:@&quot;NO&quot;,[NSThread currentThread]);
}];
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">2018-05-09 18:31:25.808197+0800 OCProject[923:284717] sort:0 0 -- 0 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.808692+0800 OCProject[923:284717] sort:0 1 -- 1 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.808975+0800 OCProject[923:284717] sort:0 2 -- 2 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.809250+0800 OCProject[923:284717] sort:0 3 -- 3 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.809499+0800 OCProject[923:284717] sort:0 4 -- 4 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.809890+0800 OCProject[923:284717] sort:1 0 -- 0 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.810140+0800 OCProject[923:284717] sort:1 1 -- 1 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.810388+0800 OCProject[923:284717] sort:1 2 -- 2 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.810635+0800 OCProject[923:284717] sort:1 3 -- 3 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.810883+0800 OCProject[923:284717] sort:1 4 -- 4 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.813959+0800 OCProject[923:284717] sort:2 0 -- 0 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.814289+0800 OCProject[923:284717] sort:2 1 -- 1 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.814552+0800 OCProject[923:284717] sort:2 2 -- 2 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.814806+0800 OCProject[923:284717] sort:2 3 -- 3 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
2018-05-09 18:31:25.815054+0800 OCProject[923:284717] sort:2 4 -- 4 --- YES --- &lt;NSThread: 0x137e0bb50&gt;{number = 1, name = main}
</code></pre>

<p>当我把数组内的元素个数增加到 10，请看前缀是<code>sort:1</code> 的打印结果如下：</p>

<pre><code class="language-text">2018-05-09 18:34:41.806499+0800 OCProject[928:286028] sort:1 0 -- 0 --- YES --- &lt;NSThread: 0x145e0bb50&gt;{number = 1, name = main}
2018-05-09 18:34:41.806982+0800 OCProject[928:286068] sort:1 1 -- 1 --- YES --- &lt;NSThread: 0x145eb08d0&gt;{number = 3, name = (null)}
2018-05-09 18:34:41.809488+0800 OCProject[928:286068] sort:1 3 -- 3 --- YES --- &lt;NSThread: 0x145eb08d0&gt;{number = 3, name = (null)}
2018-05-09 18:34:41.809518+0800 OCProject[928:286028] sort:1 2 -- 2 --- YES --- &lt;NSThread: 0x145e0bb50&gt;{number = 1, name = main}
2018-05-09 18:34:41.809788+0800 OCProject[928:286068] sort:1 4 -- 4 --- YES --- &lt;NSThread: 0x145eb08d0&gt;{number = 3, name = (null)}
2018-05-09 18:34:41.809840+0800 OCProject[928:286028] sort:1 5 -- 5 --- YES --- &lt;NSThread: 0x145e0bb50&gt;{number = 1, name = main}
2018-05-09 18:34:41.810045+0800 OCProject[928:286068] sort:1 6 -- 6 --- YES --- &lt;NSThread: 0x145eb08d0&gt;{number = 3, name = (null)}
2018-05-09 18:34:41.810462+0800 OCProject[928:286028] sort:1 7 -- 7 --- YES --- &lt;NSThread: 0x145e0bb50&gt;{number = 1, name = main}
2018-05-09 18:34:41.810989+0800 OCProject[928:286068] sort:1 8 -- 8 --- YES --- &lt;NSThread: 0x145eb08d0&gt;{number = 3, name = (null)}
2018-05-09 18:34:41.811034+0800 OCProject[928:286028] sort:1 9 -- 9 --- YES --- &lt;NSThread: 0x145e0bb50&gt;{number = 1, name = main}
</code></pre>

<h3 id="toc_14">遍历字典</h3>

<pre><code class="language-text">// 主线程 无序
[_dataDic enumerateKeysAndObjectsUsingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
    NSLog(@&quot;key:%@ -- value:%@  --- %@&quot;,key,obj,[NSThread currentThread]);
}];
    
// 无序； NSEnumerationReverse反向遍历，并发遍历 NSEnumerationConcurrent

[_dataDic enumerateKeysAndObjectsWithOptions:NSEnumerationReverse usingBlock:^(id  _Nonnull key, id  _Nonnull obj, BOOL * _Nonnull stop) {
    NSLog(@&quot;key:%@ -- value:%@  --- %@&quot;,key,obj,[NSThread currentThread]);
}];
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">2018-05-09 18:33:48.223268+0800 OCProject[926:285509] key:3 -- value:我是第3个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.224066+0800 OCProject[926:285509] key:1 -- value:我是第1个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.225122+0800 OCProject[926:285509] key:4 -- value:我是第4个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.226368+0800 OCProject[926:285509] key:2 -- value:我是第2个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.226915+0800 OCProject[926:285509] key:0 -- value:我是第0个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.227419+0800 OCProject[926:285509] key:3 -- value:我是第3个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.228593+0800 OCProject[926:285509] key:1 -- value:我是第1个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.229978+0800 OCProject[926:285509] key:4 -- value:我是第4个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.231440+0800 OCProject[926:285509] key:2 -- value:我是第2个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
2018-05-09 18:33:48.231977+0800 OCProject[926:285509] key:0 -- value:我是第0个Item  --- &lt;NSThread: 0x107e0b250&gt;{number = 1, name = main}
</code></pre>

<h3 id="toc_15">【分析】</h3>

<ul>
<li>优点：
<ul>
<li>遍历时可以直接从block中获得需要的所有信息，包括下标、值等。特别相对于字典而言，不需要做多余的编码即可同时获得key和value的值。</li>
<li>能够直接修改block中key或者obj的类型为真实类型，可以省去类型转换的工作。</li>
<li>可以通过NSEnumerationConcurrent枚举值开启并发迭代功能。</li>
</ul></li>
<li> 缺点：暂无<br/>
&gt; 说明：基于Block的遍历方式在实现反向遍历的时候也非常简单，使用enumerateObjectsWithOptions方法，传递NSEnumerationReverse作为参数即可，在处理遍历操作的时候推荐基于Block的遍历方式。</li>
</ul>

<h2 id="toc_16">迭代</h2>

<h3 id="toc_17">遍历数组</h3>

<pre><code class="language-text">dispatch_queue_t queue =dispatch_queue_create(&quot;apply并行队列&quot;, DISPATCH_QUEUE_CONCURRENT);
dispatch_apply(_dataSource.count, queue, ^(size_t index) {
    NSLog(@&quot;%@----%@&quot;,self-&gt;_dataSource[index],[NSThread currentThread]);
});
NSLog(@&quot;end1&quot;);
</code></pre>

<h3 id="toc_18">遍历字典</h3>

<pre><code class="language-text">NSArray *allkeys = [_dataDic allKeys];
NSArray *allValue = [_dataDic allValues];
dispatch_apply(_dataDic.count, queue, ^(size_t index) {
    NSString *key = [allkeys objectAtIndex:index];
    NSLog(@&quot;dic: %@----%@&quot;,[self-&gt;_dataDic objectForKey:key],[NSThread currentThread]);
});
</code></pre>

<p>打印结果：</p>

<pre><code class="language-text">2018-05-09 19:24:03.875390+0800 OCProject[975:301673] 0----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.875913+0800 OCProject[975:301673] 2----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.876194+0800 OCProject[975:301673] 3----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.876445+0800 OCProject[975:301673] 4----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.876688+0800 OCProject[975:301673] 5----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.876926+0800 OCProject[975:301673] 6----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.877162+0800 OCProject[975:301673] 7----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.877398+0800 OCProject[975:301673] 8----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.877669+0800 OCProject[975:301673] 9----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.878021+0800 OCProject[975:301852] 1----&lt;NSThread: 0x1231b4750&gt;{number = 3, name = (null)}
2018-05-09 19:24:03.878310+0800 OCProject[975:301673] end1
2018-05-09 19:24:03.878752+0800 OCProject[975:301673] dic: 我是第7个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.879072+0800 OCProject[975:301673] dic: 我是第3个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.879372+0800 OCProject[975:301673] dic: 我是第8个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.879672+0800 OCProject[975:301673] dic: 我是第4个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.879971+0800 OCProject[975:301673] dic: 我是第0个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.880271+0800 OCProject[975:301673] dic: 我是第9个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.880568+0800 OCProject[975:301673] dic: 我是第5个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.883701+0800 OCProject[975:301673] dic: 我是第6个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.883947+0800 OCProject[975:301673] dic: 我是第2个Item----&lt;NSThread: 0x121e0ba50&gt;{number = 1, name = main}
2018-05-09 19:24:03.880890+0800 OCProject[975:301852] dic: 我是第1个Item----&lt;NSThread: 0x1231b4750&gt;{number = 3, name = (null)}
</code></pre>

<h3 id="toc_19">【分析】</h3>

<ul>
<li>优点：开启多条线程并发处理遍历任务，执行效率高。</li>
<li>缺点：
<ul>
<li>对于字典和集合的处理需借助数组 </li>
<li>无法实现反向遍历。</li>
</ul></li>
</ul>


    

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